1. Field of the Invention
The present invention relates to a collimating optical system for collimating a diversing light beam emitted from a light source such as semiconductor laser or LD, and more particularly to a high performance collimating optical system which uses a spherical lens.
2. Related Background Art
In a precision equipment such as a laser beam printer, a collimating optical system for collimating a laser beam emitted from a laser is used.
In such a collimating optical system, since it is necessary to limit a wavefront aberration to less than a quarter of wavelength, a plurality of lenses are usually used or a non-spherical lens is used to attain a desired performance.
However, since the collimating optical system comprising a plurality of lenses imposes severe requirements for glass work and assembly precision, manufacturing and adjustment times are long and mass-productivity is not high.
In the collimating optical system which uses the non-spherical lens, a desired performance may be attained by a single lens but a non-spherical plane precision is severe and non-spherical polishing and non-spherical molds are difficult to attain. Further, a yield in mass production is not high.